1 /* Return size of GNU compressed section.
2 Copyright (C) 2015 Red Hat, Inc.
3 This file is part of elfutils.
4
5 This file is free software; you can redistribute it and/or modify
6 it under the terms of either
7
8 * the GNU Lesser General Public License as published by the Free
9 Software Foundation; either version 3 of the License, or (at
10 your option) any later version
11
12 or
13
14 * the GNU General Public License as published by the Free
15 Software Foundation; either version 2 of the License, or (at
16 your option) any later version
17
18 or both in parallel, as here.
19
20 elfutils is distributed in the hope that it will be useful, but
21 WITHOUT ANY WARRANTY; without even the implied warranty of
22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 General Public License for more details.
24
25 You should have received copies of the GNU General Public License and
26 the GNU Lesser General Public License along with this program. If
27 not, see <http://www.gnu.org/licenses/>. */
28
29 #ifdef HAVE_CONFIG_H
30 # include <config.h>
31 #endif
32
33 #include "libdwelfP.h"
34 #include "libelfP.h"
35
36 ssize_t
dwelf_scn_gnu_compressed_size(Elf_Scn * scn)37 dwelf_scn_gnu_compressed_size (Elf_Scn *scn)
38 {
39 if (scn == NULL)
40 return -1;
41
42 GElf_Shdr shdr;
43 if (gelf_getshdr (scn, &shdr) == NULL)
44 return -1;
45
46 /* Allocated or no bits sections can never be compressed. */
47 if ((shdr.sh_flags & SHF_ALLOC) != 0
48 || shdr.sh_type == SHT_NULL
49 || shdr.sh_type == SHT_NOBITS)
50 return -1;
51
52 Elf_Data *d = elf_rawdata (scn, NULL);
53 if (d == NULL)
54 return -1;
55
56 if (d->d_size >= 4 + 8
57 && memcmp (d->d_buf, "ZLIB", 4) == 0)
58 {
59 /* There is a 12-byte header of "ZLIB" followed by
60 an 8-byte big-endian size. There is only one type and
61 alignment isn't preserved separately. */
62 uint64_t size;
63 memcpy (&size, d->d_buf + 4, sizeof size);
64 size = be64toh (size);
65
66 /* One more sanity check, size should be bigger than original
67 data size plus some overhead (4 chars ZLIB + 8 bytes size + 6
68 bytes zlib stream overhead + 5 bytes overhead max for one 16K
69 block) and should fit into a size_t. */
70 if (size + 4 + 8 + 6 + 5 < d->d_size || size > SIZE_MAX)
71 return -1;
72
73 return size;
74 }
75
76 return -1;
77 }
78